Click the thing ;) You can scroll or use the up/down arrow keys to look around in the shop. In the shop, you see stuff with ??? :) ???. If you have enough money, you will see the coloured form of the upgrade. (That also means that you can buy it). You can customize the backround and clicker by going to the customizer at the top left corner.
I used a bouncing effect from griffpatch's geometry dash tutorial.
